HP-67 bouncing keys

[Kees Bouw]

(09-28-2021 05:38 PM)Geoff Quickfall Wrote:  I only do this if the soap solution, followed by water rinse, followed by IPA (99%) rinse and thorough drying, application of de-oxit gold does not resolve the bounce AND if no sulphate (blue) corrosion is present. And of course cut a new plastic spill sheet using the original as a template.

If you have access to an ultrasonic cleaner (they are cheap) use it. However, I have seen thick blue sulphates emanating from the contacts.

Hi Geoff,

It is probably caused by English not being my native tongue, but I still don't understand what you mean exactly by "rinse". Do you pour a liter of IPA over the keyboard? Do you dip the keyboard in a IPA bath?

A new plastic spill sheet is hard to find. None of the plastics I found are suitable, they are either too thick or too thin or too hard or too soft. It has to be pretty strong because it sits between the keys and the metal domes. So far I have always put the original back after cleaning it thoroughly.

I don't think an ultrasonic cleaner is cheap, at least not if you want a good one. I suspect the really cheap ones are rubbish and a good one could cost 200 to 400 euros. The thick blue sufphates, was that before or after using the ultrasonic cleaner? In other words, can ultrasonic cleaning cause these sulphates to be created?

Thanks again for all your help.

Kees.